Unit 3 Ecosystems PDF

Unit3- Ecosystems 1  What is an Ecosystem? is a community or group of living organisms that live in and interact with each other in a specific environment. For instance, tropical forests are ecosystems made up of living beings such as trees, plants,...

Unit3- Ecosystems 1  What is an Ecosystem? is a community or group of living organisms that live in and interact with each other in a specific environment. For instance, tropical forests are ecosystems made up of living beings such as trees, plants, animals, insects, and micro-organisms that are in constant interaction between themselves and that are affected by other physical (sun, temperature) or chemical (oxygen or nutrients) components. The biotic and abiotic components are linked together through nutrient cycles and energy flows. 2 Classification of Ecosystem 3  Ecosystem Degradation Ecosystems are frequently disrupted by human actions which lead to the extinction of plant and animal species living only in the different natural ecosystems. Some species if eliminated seriously affect the ecosystem. These are called ‘keystone’ species. Ex: Bees. Extinction occurs due to - changes in land use. For example-Forests are deforested for timber, wetlands are drained to create more agricultural land and semi arid grasslands that are used as pastures are changed into irrigated fields. - Pollution from industry and waste from urban settings - The reason for the depletion of natural resources is twofold – our rapidly exploding population that needs to sustain itself on resources, and the growth of affluent societies, which consume. 4 Structure of Ecosystem 5 Biotic Components of Ecosystem 6 Abiotic Components of Ecosystem Physical components Chemical components 7  Function of an Ecosystem 1) Energy cycles. 2) Food chains. 3) Diversity-interlinkages between organisms. 4) Nutrient cycles- biogeochemical cycles. 5) Evolution. 8  Energy Flow in the Ecosystem Energy flow in every ecosystem is controlled by the following cycles- 1) Water cycle 2) Carbon cycle 3) Oxygen cycle 4) Nitrogen cycle 5) Energy cycle All the functions of the ecosystem are in someway related to the growth and regeneration of its plant and animal species. These linked processes can be depicted as the various cycles. These processes depend on energy from sunlight. 9 Water Cycle 10 Carbon Cycle The carbon, which occurs in organic compounds, is included in both the abiotic and biotic parts of the ecosystem. Carbon is a building block of both plant and animal tissues. In the atmosphere, carbon occurs as carbon dioxide(CO2). Through the process of photosynthesis , plants form carbohydrates that contain carbon and release oxygen into the atmosphere used by animals for respiration. 11 Carbon Cycle (contd..) Both plants and animals release carbon dioxide during respiration. Carbon is returned in the form of the waste they excrete. When plants and animals die they return their carbon to the soil. These processes complete the carbon cycle. 12 Oxygen Cycle Oxygen is taken up by plants and animals from the air during respiration. The plants return oxygen to the atmosphere during photosynthesis. This links the Oxygen Cycle to the Carbon Cycle. 13  Nitrogen Cycle About 78% of Earth’s atmosphere is Nitrogen, in free form. Living things require nitrogen in compound form (not in free form), to build proteins and other important chemicals. Not all the nitrogen that gets fixed is used by plants and animals. Some of it is returned to the atmosphere through a process called denitrification 14 Nitrogen Cycle (contd…) Bacterial species such as Pseudomonas and Clostridium perform denitrification of nitrates in anaerobic conditions (absence of oxygen). They use the nitrate in the place of oxygen during respiration. Effectively, they breathe nitrate and exhale nitrogen gas back into the atmosphere. 15 Energy Cycle The ultimate source of energy (for most ecosystems) is the Sun. The ultimate fate of energy in ecosystems is for it to be lost as heat. Energy and nutrients are passed from organism to organism through the food chain as one organism eats another. Decomposers remove the last energy from the remains of organisms. Inorganic nutrients are cycled, energy is not. Flow of energy in an ecosystem is uni- directional. 16  Energy Cycle Flow of energy in an ecosystem is governed by laws of thermodynamics, which are: Energy cannot be created or destroyed (but it can be transformed into stored energy & heat). Energy is lost as energy is transformed Integration of Cycles in Nature All these cycles are responsible for maintenance of life on earth. If mankind disturbs these cycles beyond the limits that nature can not sustain, they will eventually break down and lead to a degraded earth on which man will not be able to survive. 17 18  Ecological Succession It is the slow and gradual process, by which ecosystems change and develop over time. Ecological succession is the changing sequence of communities that live in an ecosystem during a given time period. It is the gradual replacement of one community by another through natural processes over time. For example, a bare patch of ground will not stay bare. It will rapidly be colonized by a variety of plants. It is the transition that takes place when one biotic community gives way to another biotic community. 19 Primary Succession The development of an ecosystem in an area that has never had a community living within it occurs by a process called primary succession. 20 Secondary Succession Secondary succession is the process by which an ecosystem that has been destroyed (by a disturbance such as a fire, tornado, etc...) gradually returns to its previous state. 21  Food Chains “There is a sequence of eating and being eaten in an ecosystem is known as food chain” (or) “Transfer of food energy from the plants through a series of organisms is known as food chain”. A food chain always starts with plant life and ends with animal. When the organisms die, they are all decomposed by microorganism (bacteria and fungi) into nutrients that can again be used by the plants. At each and every level, nearly 80-90% of the potential energy gets lost as heat for daily activities. 22 23 24 Tropic Levels Tropic Levels (T1,T2, T3, T4, T5) (or) Feeding levels The various steps through which food energy passes in an ecosystem is called as tropic levels. The tropic levels are arranged in the following way, The green plants or producers represent first tropic level T1, The herbivores or primary consumers represent second tropic level T2. The carnivores or secondary consumers represent third tropic level T3. The tertiary consumers are fourth tropic level T4. Finally decomposers represent last tropic level T5. 25 26 Food chains are classified into two main types 1. Grazing food chain 2. Detritus food chain Grazing food chain: Found in Grassland ecosystems and pond ecosystems. Grazing food chain starts with green plants (primary producers) and goes to decomposer food chain or detritus food chain through herbivores and carnivores. Detritus food chain: Found in Grassland ecosystems and forest ecosystems. Detritus food chain starts with dead organic matter (plants and animals) and goes to decomposer food chain through herbivores and carnivores. 27 Food Web The interlocking pattern of various food chains in an ecosystem is known as food web. In a food web many food chains are interconnected, where different types of organisms are connected at different tropic levels, so that there are a number of opportunities of eating and being eaten at each tropic level. Grass may be eaten by insects, rats, deer's, etc., these may be eaten by carnivores (snake, fox, tiger). Thus there is a interlocking of various food chains called food webs 28 29 Food Chain vs Food Web Major difference: In a linear food chain if one species gets affected (or) becomes extinct, then the species in the subsequent tropic levels are also affected. But, in a food web, if one species gets affected, it does not affect other tropic levels so seriously. There are number of options available at each tropic level. 30 Significance of Food Chains and Food Webs Food chains and food webs play a very important role in the ecosystem. Energy flow and nutrient cycling takes place through them. They maintain and regulate the population size of different tropic levels, and thus help in maintaining ecological balance. They have the property of bio-magnification. The non – biodegradable materials keep on passing from one tropic level to another. At each successive tropic level, the concentration keep on increasing. This process is known as bio-magnification. 31 Ecological Pyramids “Graphical representation of structure and function of tropic levels of an ecosystem, starting with producers at the bottom and successive tropic levels forming the apex is known as an ecological pyramid.” In food chain starting from the producers to the consumers, there is a regular decrease in the biomass and number of the organisms. Since energy is lost as heat in each tropic levels, it becomes progressively smaller near the top. Types of Ecological pyramids: 1. Pyramid of numbers. 2. Pyramid of energy. 3. Pyramid of biomass. 32 Pyramids of Numbers It represents the number of individual organisms present in each tropic levels. Ex: A grassland Ecosystem The producers in the grasslands are grasses, which are in size and large in numbers. So the producers occupy lower tropic level (1St tropic level). The primary consumers (herbivores) are rats, the 2nd tropic level. Since the number of rats are lower Compared to the grasses, the size is small. The secondary consumers (carnivores) are snakes, which occupy the 3rd tropic level. Since the number of snakes are lower when compared to the rats. The tertiary consumers (carnivores) are eagles, which the next tropic level. The number and size of the last level is till smaller. 33 34 35  It represents the total amount of biomass (mass or weight of biological material or organism) present in each tropic levels. Ex: A forest ecosystem The above figure shows that there is a decrease in the biomass from the lower tropic level to the higher tropic level. This because the trees (producers) are maximum in the forest, which contribute a huge biomass. The next tropic levels are herbivores (rabbit, deer) and carnivores (snakes, fox). Top of the tropic level contains few tertiary consumers (lion, tiger), the biomass of which is very low. 36 Pyramid of Energy This pyramid indicates not only the amount of energy flow at each level, but more importantly, the actual role the various organisms play in the transfer of energy. An energy pyramid illustrates how much energy is needed as it flows upwards to support the next trophic level. Always there is a huge loss of energy. 37  Forest Ecosystem A forest is an area with a high density of trees. A forest ecosystem is one in which tall trees grow that support many animals and birds. The forests are found in undisturbed areas receiving moderate to high rainfall. The forest occupies nearly 31% of the world’s land, in India it is only 19% of total land area. 39 Types of forest ecosystem Based upon the climate conditions, forests are classified into: Tropical Rain forests. Tropical deciduous forests. Temperate rain forests. Temperate deciduous forests. 40 Characteristics of forest ecosystems Forests are characterized by warm temperature and adequate rainfall, which make the generation of number of ponds, lakes etc., The forest maintains climate and rainfall. The forest support many wild animals and protect biodiversity. The soil is rich in organic matter and nutrients which support the growth of trees. 41 42 Grassland Ecosystem Grassland occupies about 20% of earth’s surface. In addition to grass some trees and shrubs are/also present in grasslands. Limited grazing helps to improve the net primary production of the grasslands. But, overgrazing leads degradation of these grasslands resulting in desertification. Types of grassland ecosystem Depending upon the climate conditions grassland are classified into three types 1. Tropical grasslands 2. Temperate grasslands 3. Polar grasslands 43 44 Features of different types of grassland Tropical grasslands They are found near the borders of tropical rain forests. Characterized by high temperature and moderate rainfall (40 to 100 cm). It is also known as Savanna type. Tall grasses with scattered shrubs and stunted trees and animals like zebras, giraffes, antelopes, etc., are observed here. Temperate grasslands They are usually found in the centers of continents, highly sloped hills. They are characterized by very cold winters and hot summers. Intense grazing and summer fires, do not support shrubs or trees to grow. 45 Polar grasslands They are found in arctic polar regions. They are characterized by severe cold and strong winds along with ice and snow. In summers several small annual plants grow. There are animals like arctic wolf, weasel, arctic fox, etc., Characteristics of Grassland Ecosystems 1. Grassland ecosystem is a plain land occupied by grasses. 2. Soil is very rich in nutrients and organic matter. 3. Since it has tall grass, it is ideal place for grazing animals. 4. It is characterized by low or uneven rainfall. 46 Desert Ecosystem Desert occupies about 14% of our world’s land area. It is characterized by less than 25 cm rainfall. The atmosphere is dry and hence it is a poor insulator. Types of desert ecosystems Based on the climatic conditions, deserts are classified into three types. 1. Tropical deserts. 2. Temperate deserts. 3. Cold deserts. 47 48  Features of different types of deserts Tropical desert is an environment of extremes, it is the driest and hottest place on earth. Rainfall is sporadic and in some years no measurable precipitation falls at all. 1. Africa: Sahara desert. 2. Rajasthan: Thar desert. Temperate desert is a barren area of land where little precipitation occurs (less than 10%), characterized by very hot summer and very cold Winter time. Ex: Atacama, Mojave. Cold deserts have hot summers but extremely cold winters. These are found in high, flat areas, called plateaus. Ex: Gobi desert, Ladakh. 49 50 Aquatic Ecosystems The aquatic ecosystem deals with water bodies. The major types of organisms found in aquatic environments are determined by the water’s salinity. Types of aquatic life zone Aquatic life zones are divided into two types. 1. Fresh water life zones Eg. Ponds, streams, lakes, rivers. 2. Salt water life zones Eg. Oceans, estuaries. 51 Fresh Water Ecosystem – Pond Ecosystem A pond is a fresh water aquatic ecosystems, where water is stagnant. It receives enough water during rainy season. It contains several types of algae, aquatic plants, insects, fishes and birds. Characteristics of pond 1. Pond is temporary, only seasonal. 2. It is a stagnant fresh water body. 3. Ponds get polluted easily due to limited amount of water. 4. Pond ecosystems are lentic ecosystems – i.e. they involve stagnant or standing water. 52 Lake Ecosystem Lakes are large natural shallow water bodies. Lakes are used for various purposes. Lakes are supplied with water from rainfall, melting snow and streams. Types of lakes Some important types of lake are Oligotrophic lakes : They have low nutrient concentrations Eutrophic lakes : They are over nourished by nutrients like N and P Dystrophic lakes : They have low pH, high humid content and brown waters. 53 River Ecosystem The running water of a stream or a river is usually well oxygenated, because it absorbs oxygen from the air. The number of animals are low in river or stream. Characteristics of River or Stream. It is a fresh water, and free flowing water systems. Due to mixing of water, dissolved oxygen content is more. River deposits large amount of nutrients. 54  Salt Water Ecosystem – Ocean Ecosystem Oceans cover more than two thirds of the earth’s surface. Ocean environment is characterized by its high concentration of salts and minerals. It supplies huge variety of products and drugs. It also provides us iron, magnesium, iron, natural gas. Zones of Oceans The oceans have two major life zones. Coastal zone: It is relatively warm, nutrient rich shallow water. It has high primary productivity because of high nutrients and sunlight. Open sea: It is the deeper part of the ocean. It is vertically divided into three regions. 1. Euphotic zone: It receives abundant light and shows high photosynthetic activity. 2. Bathyal zone: It receives dim light and is usually geologically active. 3. Abyssal zone: It is the dark zone and is very deep (2000 metres). 55 56 Thank You 57